Induction heating coil provided with stress-relieving supports



Jan. 4,1949. H. A. STRICZKLAND, JR

INDUCTION HEATING COIL PROVIDED WITH STRESS-RELIEVING SUPPORTS 2 Sheets-Sheet 1 Filed. Oct. 15, 1944 INVENTOR HAROLD A. STRICKLAND JR.

BY W ATTORNEY Jan. 4, 1949. H. A. STRICKLAND, JR

INDUCTION HEATING COIL: PROVIDED WITH STRESS-RELIEVING SUPPORTS 2 Sheet-Sheet 2 Filed 001;. 13, 1944 FIG?) INVENTOR HAROLD A.STR1CK'LAND JR.

ATTORNEY Patented Jan. 4, 1949 INDUCTION HEATING COIL YROVIDED WITH STRESS ItELIEVING SUPPORTS Harold A. Strickland, Jr., Detroit, Mich, Sim,

by mesne assignments, to The Ohio Crankshaft Ohio, n corporation of Company, Cleveland, 'Ohio Application o tom- 13, 1344, Serial No. 553,504

5 Claims. 1

This invention relates to induction heating apparatus.

A usual form of induction heating apparatus consists in a single primary coil having adjacent attachment ends for the bus bar connection and a central support upon which the workpiece is mounted in heating relationship with the coil, the workpiece acting as a secondary and thereby receiving heat energy inductively from the primary coil. It is usual in heaters of this type to support the primary coil rigidly. A disadvantage of this construction as developed in use arises from the fact that, due to the continuous heating and cooling of the coil area on the inner periphery thereof, a state of fatigue develops'which finally results in cracking of the coil at approximately the highest stressed point of the circuit. At the development of a minute crack the resulting current concentration at the crack makes the failure progressively rapid. This failure, resulting from the heating and cooling stresses on the coil, is reasonable to expect when it is considered that the inner surface of the, coil receives the maximum amount of heat during power applications and subsequent drastic cooling with the passage of quench liquid and hence an extreme range of hot and cold is effective in this inner surface. 1

It is accordingly an important object 'ofthe present invention to provide a heating coil construction which will tend to eliminate the formation of stress fissures or cracks in the coll.- Other objects inherent in the structureand related to simplicity of construction and economy of manufacture will appear on consideration of the embodiment of the invention hereinafter described and shown in the accompanying drawings, in which:

Figure 1 is an elevation partly in section of a heater coil with the associated workpiece mounted thereover, taken along line of Figure 2;

Figure 2 is a plan view of the heating unit and workpiece; and,

Figure 3 is a detail of the flexible connection between the coil attachment ends and the bus bar terminals taken along the line 3-3 of Figure 1.

Referring to Figure 1 there is shown an inductor coil I, this unit having a hollow construction to form a cavity or receptacle 2 for quench liquid. The quench inlet is indicated by the numeral 3, the outlet consisting of a series of nozzle apertures 4 in the depressed upper wall of the coil forming the contour 5 for the reception of the workpiece 6. As shown, the various nozzles 4 are substantially perpendicular to the surface of workpiece 6..

. The inductor coil is mounted on two standards I which are fixed to the base by means of threads on bolts l and N, there being provided connecting lugs l2 and I3 terminating in eyerings H and I for connection between the inductor coil and the standards 1. Insulation washers and tubes l6 and. Il insulate the standards from the support and integral lugs of the coil.

As is clearly apparent from Figure 2 of the drawing, the inductor coil is singular and terminates in attachment ends I8 and I9 which are laminated sheets bent into U-shape with the ends thereof connected directly to the attachment ends of the coil'and the bus bar terminals as shown clearly in Figure 3 of the drawing. Bolts 24 serve to hold the strip ends in position. Flexible pipe connections 25 are also utilized to connectithe coolant spaces in the attachment ends l8 and W of the coil to spaces provided in the bus bar terminals and 2|. Nozzles 4| are also provided to spray a continuous cooling stream on the flexible conductors 22 and 23. The bus bar terminals 20, 2| are attached by suitable means to fixed bus bars having fluid connections.

The workpiece-6, which is shown as a wheel hub, is supported from the base 8 by a standard 25 having an internally threaded extension 21 penetrating the central area of the coil and in which is adapted to be inserted a removable support plate 28. This support plate is provided on its base side with a threaded projection 29 adapted to engage the extension 21 of the support as shown in Figure 1 and an upper extension 30 also externally threaded which is adapted to receive the end clamp 3| with the manual hand grip 3'2 thereon. By removal of the clamp 3|, the workpiece may be positioned upon the plate 28 and the clamp re-applied and tightened to hold the workpiece rigidly in heating relation to the contour 5 of the heating coil.

It now appears from the description and from the showing, particularly of Figure 2, that the heating coil is rigidly mounted upon the base 8 only by means of the standards 1 the attachment ends I8 and I9 being, within limits, free and move inwardly and outwardly under the action and contraction of the interior heated metal surface of the coil is permitted to have free play sufficient to prevent the fatigue stresses normally formed adjacent the point indicated by the numeral 33. It will be noted, especially from Fig. 2, that the point or points of support provide movement of portions of the inductor about a line or lines parallel with the axis of curvature of the inductor; also that when more than one point of support is provided the points of support are angularly spaced about the inductor axis; and further, that all points of support lie within an angle or are of less than 180 degrees so as not to constrict the expansion and contraction of the coil within a non-expansible sector. The points of support are spaced away from a free end at such minimum distance as will allow the end to have a considerable length for free movement. In the case where both ends are free the point of support is preferably placed on the opposite side, and where the support is at a plurality of points for stability, these are preferably arranged symmetrically with respect to the free ends. By this means, therefore, premature leakage of the coil prevented and the coil is preserved for a substantial period of usefulness. By tests in actual use the coil life has been extended from about one week to an indefinite period of six or eight months or longer.

A specific type of heating coil is shown as applied to a wheel hub but obviously changes of a minor nature may be made to adapt the apparatus to workpieces of different types and hence .no limitation is implied by the specific illustra- ,tive showing, other than may be required by the scope of the claims hereto appended.

What is claimed is:

1. In an induction heater, a base, a single heating coil having attachment ends, coil support means between the coil and base only at the coil side opposite to the attachment ends, fixed bus bar terminals, and flexible electrical connections between the attachment ends and terminals.

2. In an induction heater in combination, a fixed supporting base means, a curved open-sided continuous inductor which is subject to expansion and contraction as a whole relative to its axis of curvature with temperature changes, said inductor having two adjacent independent ends which 4 are spaced apart and which have permissible movement relative to each other upon expansion or contraction of the inductor, electrical connections for both of said inductor ends, the connections for at least one of said ends providing free movement thereof about the axis of the inductor, and relatively fixed support means at one or more points between said inductor and said base means, the point of support nearest a flexible end .being located at such a minimum distance therefrom as to permit it to have free movement, said support means at each point of independent support providing turning movement for portions of said inductor relative thereto about a line parallel with the axis of the inductor, and in the case where support is provided at a plurality of points these points being angularly spaced apart but all lying within an arc of not over 180 degrees of curvature, whereby the said ends of the inductor are permitted to have free movement relative to each other and the inductor is relatively free to expand and contract without rigid constriction.

3. An induction heater as set forth in claim 2, wherein the inductor has a curvature of over 180 degrees.

4. An inductor heater as set forth in claim 2, wherein both ends of the inductor have flexible electrical connections and are free to move about the axis of the inductor, and in which said support means is provided on the portion of the inductor opposite the free ends.

5. An inductor heater as set forth in claim 2, wherein both ends of the inductor have flexible electrical connections and are free to move about the axis of the inductor, and in which said support means is provided on the portion of the inductor opposite the free ends, said support means providing support at two spaced points symmetrically arranged relative to the said ends.

HAROLD A. STRICKLAND, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,813,591 Ulrey July 7, 1931 1,904,214 Fagan Apr. 18, 1933 2,170,700 Von Henke Aug. 22, 1939 2,223,970 Stansel Dec. 3, 1940 2,271,916 Denneen et al Feb. 3, 1942 2,348,361 Rudd et a1 May 9, 1944 FOREIGN PATENTS Number Country Date 117,663 Australia Nov. 4, 1943 

